The present invention relates to a steel laminate gasket for an internal combustion engine with auxiliary combustion chambers as well as cylinder bores to prevent leakage of gas from the cylinder bores and the auxiliary combustion chambers.
One example (prior art) of an engine with an auxiliary combustion chamber and a steel laminate gasket therefor is shown in FIGS. 1 and 2. In this engine, a cylinder head H is provided with an auxiliary combustion chamber M, to which a mouth plate L is attached to define the auxiliary combustion chamber M. A gasket 10 is installed between a cylinder block J and the cylinder head H with a part of the mouth plate L.
In this engine, since only a part of the mouth plate L is supported by the gasket 10 on the cylinder block J, when the engine is operated, the mouth plate L is liable to move. As a result, combustion gas from the cylinder bore is also liable to leak, especially from points N, N' where an outer portion of the mouth plate L contacts an inner surface of the cylinder bore Hc.
In order to prevent leakage from the cylinder bore Hc, there have been proposed various methods.
In the gasket 10 as shown in FIGS. 1 and 2, the gasket 10 includes cylinder bores Hc, water holes Hw, oil holes Ho, push rod holes Hp and bolt holes Hb. The gasket 10 is formed of plates 11, 12, 13, 14, 15, and a wire ring 16. The plate 11 has a curved portion 11a around the cylinder bore Hc, and a flange 11b situated outside the plate 15. The plate 12 includes a bead 12a around the cylinder bore Hc, and a bead 12b outside a counter portion P corresponding to the mouth plate L. The wire ring 16 is situated adjacent to the curved portion 11a to surround the cylinder bore Hc.
In the gasket 10, the beads 12a, 12b are formed outside the cylinder bore Hc and the counter portion P. However, when the mouth plate L is slightly moved, combustion gas may leak through the beads 12a, 12b.
In U.S. Pat Nos. 4,791,897, 4,803,965 and 4,809,653, additional beads are further provided, such as beads outside connecting or intersecting points of the beads 12a, 12b, with one or more bead located inside the counter portion P. Height and orientation of the beads may also be changed.
The gaskets as proposed in these patents substantially prevent leakage of combustion gas from the cylinder bores. However, in case compression ratio is extremely high or the mouth plate L is liable to move, the gaskets as proposed in the patents do not operate as intended.
On the other hand, Japanese Patent Publication (KOKAI) No. 61-255254 proposed a gasket having an outer bead in the form of a step to provide tightening pressure equally on all beads and to improve sealing ability. Since the outer bead or step is formed along an outer edge of a gasket, if leakage happens at a high pressure portion, the outer bead can not stop leakage.
The present invention has been made in view of the above prior art.
One object of the present invention is to provide a steel laminate gasket, which can tightly seal around a cylinder bore with an auxiliary combustion chamber.
Another object of the invention is to provide a steel laminate gasket as stated above, wherein even if leakage occurs at main sealing means, the leakage is sufficiently prevented.
A further object of the invention is to provide a steel laminate gasket as stated above, wherein the gasket can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.